Really? Odd. I just tried it with 10 random web proxies and it worked for 8 out of the 10 (the bx3 one below sort of worked, but page lay out got really garbled; and the 70.85.216.247 one just sent me an ad and not the mininova page):

Have you tried the randomize feature on proxy.org? Jay just tested it about 25 times and got different IPs from each one that worked. Only 1/2 of them worked, but it did seem to work pretty well. Jay is thinking that proxy.org and the similar sites are only helpful for posting to different sites from post to post, so that the site wouldn't identify that a bunch of torrents came from the same IP.